Marlon Mack is the promising rookie, the 21-year old who has intermixed flashes of his big-play skills with stretches of ineffectiveness.

With Turbin out of the mix, it most definitely will be the Frank and Mack Attack. The only other healthy running backs are Matt Jones, an imposing 239-pounder who’s rushed 5 times for 14 yards, and Josh Ferguson, who was added to the active roster from the practice squad Friday.

Essentially, it’s Frank and Mack.

“Me and Marlon got a bigger role to fill,’’ Gore acknowledged. “We’ve just got to be ready for it.

“It’s tough losing Turbo. He has done a lot for this offense, especially on third down. He’s a great protector, catches the ball out of the backfield, tough player. It’s a big test for us.’’

Gore is off to one of the quietest six-game stretches of his career: 85 attempts, 288 yard and two touchdowns. His yardage total ranks 20th in the league and his attempts are tied for tied for 12th.

Gore is averaging 14.6 carries per game, but that’s deceptive. He shouldered 25 against the Cleveland Browns, but 12 or fewer three times.

“I’ve got to be ready for whatever,’’ he said.

It’s interesting to note Gore never has been a workhorse during his 13-year, 186-game career. He’s logged 25 or more carries just 19 times with a career-high of 31.

The issue isn’t whether Gore will be ready for what promises to be more work. He’ll probably assume much of Turbin’s third-down work.

The overriding concern: Is Mack ready for a co-starring role?

“He’ll be OK,’’ promised Gore. “Coaches will have him right.’’

Mack’s game-breaking skills at South Florida caught the eye of the Colts’ personnel staff and convinced them to invest a fourth-round pick in the April draft. He averaged 6.2 yards and generated 32 touchdowns on 586 career carries. Six of his 15 rushing TDs as a senior were 43 yards or longer.

Although a shoulder injury kept him out of two games this season, Mack’s explosiveness has been evident. Six of his 27 carries have picked up at least 10 yards, and four have gained at least 20. His four 20-plus runs equal the Colts’ total from a year ago.

What’s been missing are consistency and opportunities. Twelve of the 27 carries have been for 0 yards or a loss. And in Monday’s loss to the Titans, he had two carries for 18 yards in the first half – appropriately, a 22-yard run and the other for minus-4 – but none in the second half.

Pagano was adamant the Colts must get Mack more involved, which includes as a receiver out of the backfield. His three receptions include a 21-yard catch-and-run.

“We’ve got to get him the ball more,’’ Pagano said. “It’s on me. Yeah, and if it doesn’t (happen), then blame the coach. I screwed that up. Everything runs right through this dude right here.’’

Coordinator Rob Chudzinski attributed Mack’s disappearing act against the Titans to the offense’s inability to sustain drives. In the third quarter, the Colts’ four possessions consisted of three three-and-outs and a lost fumble. They didn’t register their initial first down of the second half until less than 9 minutes remained in the fourth quarter.

“As far as the running game goes,’’ Chudzinski said, “we just didn’t have a lot of time on the field in the second half.’’

There also were occasions when quarterback Jacoby Brissett went to the line of scrimmage with a run-pass option, and checked to a pass play because of the defense he was facing. When the Colts went up-tempo and into a 2-minute offense mode, Turbin generally was in the backfield.

With Turbin no longer an option – he is one of the NFL’s premier short-yardage backs – Mack must step up and Chudzinski must determine how best to use him.

“Losing (Turbin) will give Marlon more opportunities,’’ he said. “Again, some things like 2-minute and so forth that Turbo was in on and the guy that gets all the reps . . . we’re going to have to find between Frank and Marlon and whoever else.

“We’ll have to find guys to fill those roles.’’

An injury forced Mack to miss a portion of the offseason work and training camp, and the shoulder kept him out of the Cleveland and Seattle games. For him to adequately replace Turbin, he must prove capable of picking up the hard yards and being a reliable blocker in pass protection.

“We all prepare for the same thing,’’ said Mack. “We’re just focused on going out there and just balling out.

“With Turbin out, we just got to step up to the plate. Next man up.’’

Mack insisted he’s eager for a heavier workload.

“Got to embrace it a lot,’’ he said. “Just got to be ready whenever my name is called. Going out there with the legend Frank every day feels great.’’